Akron’s Drive to be Energy Neutral

Brian M. Gresser, P.E. Akron Water Reclamation

Bureau Manager

Thomas F. Smith, P.E. Senior Engineer

October 10, 2012/ November 2015 Modified M

Background on Akron Historical energy usage Energy-related projects Biosolids management Leveraging assets Conclusions Questions?

62.4 Square Miles Total Population

≈200,000 2008 All-America

City

Service Area 110 square miles Population served 350,000 1358 miles sewers Average daily flow 72 MGD Peak flow 280 MGD Conventional activated sludge Composting → Anaerobic

digestion

Facility served by 69,000 v feed from utility City-owned substation Previous rate structure penalized for

demand Historical monthly usage was nearly

4,000,000 kWh Monthly electricity cost was about

$220,000 (5.5 ¢/kWh)

Aeration 54.1%

Clarifiers 3.2%

Grit 1.4%

Screens 0.5%

Wastewater Pumping

14.3% Lighting & Buildings

8.1%

Chlorination 0.3%

Belt Press 3.9%

Anaerobic Digestion

13.3%

Gravity Thickening

0.1%

Return Sludge Pumping

0.8%

Derived from data from the Water Environment Energy Conservation Task Force Energy Conservation in Wastewater Treatment

Fine-pore aeration diffuser system Computerized Process Control DAF to GBT Liquid oxygen Pre-Aeration system shutdown Landfill gas to energy High speed blowers Anaerobic Digestion HVAC Upgrades to Administration Building

Replaced existing coarse

bubble diffusers 365,000 kWh /mo reduction $1.4M capital cost 6 year payback Project completed in 1995

Replaced “islands” of automatic control Rapid data transmission with fiber optic

highway DO control of aeration blowers Project completed in 1995 Stimulus project in 2010 replaced much

of the hardware and software

Waste activated sludge thickening Replaced dissolved air floatation with

gravity belt thickeners Power consumption was reduced by

about two-thirds/ polymer reduced 2/3rds & went to unmanned operation

Annual power savings of $45,000 Project completed in 1999

Minimum dissolved oxygen concentration of 5.0 mg/l

Avoidance of costly submerged aeration of 300 connected horsepower.

LO2 uses pressure in storage system No connected horsepower

Provided grease separation, grit removal, and DO enhancement

Energy savings of $120,000 annually Project completed in 2004 at a cost of

$175,000 Payback less than 2 years

Closed municipal landfill across street Private investment with federal grant

money for renewable energy projects Negotiated reduced rate for power 1.1 MW Waukesha Enginator CHP Provides 700,000 kWh/mo or 40% of total

facility load City has right to excess gas and engine

heat

Current plant aeration load is 950,000 kWh/mo or 50% of total facility load

4 new 540 hP blowers are 20% more efficient than existing centrifugal blowers

Units operate between 38% – 100% output Magnetic bearings…non-contact, non-

wear, frictionless Units cost $250k each Received $108 K in Utility Rebate payments

Blower Control Panel

Incentive-based utility reimbursement From significant energy user to net-

energy producer ADS1 ADS2

“Pilot project” to prove high-solids digester technology

Sized to process 1/3 of wwtp biosolids 335 kW Jenbacher CHPU Operational Spring 2008

Odor › Less complaints (zero)

Amendments › 2008 savings of 5,000 yds › 2009 savings of 9,500 yds › 2010 savings of 10,000

yds Chemicals

› 3,000 to 5,000 gallons less of sulfuric acid

› Polymer usage went up by 11,000 gallons

Utilities › Approximately 1,500,000

kWh less

Full-scale project to replace composting Sized for 15,000 dry tons per year 3 x 600 kW 2G Cenergy packaged CHPUs Exhaust heat recovery for sludge dryer -

400ºF thermal fluid, 92% dry solids output Operational Fall of 2013

Feedstock › Between 1,150 to 1,250 dry tons/month 20% being the raw liquid

Digested Solids › Roughly 50% across the centrifuges

500

525

550

575

600

625

650

675

0

200

400

600

800

1,000

1,200

1,400

Jan Feb Mar Apr

Dry

Tons

2014 Monthly Material Throughput

Total Dry Feed Total Liquid Feed

Material to Wells Material Across Centrifuges

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

3,500,000

4,000,000

4,500,000

1995 1997 1999 2001 2003 2005 2007 2009 2011 2013

YEAR

Computer-control of blowers and fine-pore

aeration

DAF replaced with GBT

Incentive-based utility reimbursement

ADS1 335 kW generator on-line

1.1 MW Landfill gas generator on-line

ADS2 2 x 600 kW Generators & High

Speed Blowers

kWh

Pre-aeration shutdown

Feed Rate › 35,000 gal/day of

5% solids › ~120 WT/day of 28%

solids Digested Solids

› 65,000 gal/day of 9% solids removed

CHPU › 30,000 kWh/day

produced › 5.37 MMBTU/hr

produced Dried Solids

› 35 to 40 yds/day of 90%+ pellet-like material

850,000 kWh/month capacity › Approaching 95% capacity

Real-time Pricing Demand response

24 hourly prices quoted the day ahead Range was $0.017 to $2.01 per kWh Customer Baseline Load (CBL) Ideal candidates are significant users,

stable load, ability to generate or curtail Participated in 1999 and 2000 Ended program due to declining load

from major plant modifications

Load reduction program during times of grid emergency or peak demand

Compensation for reducing load weekdays, Jun – Sept, Noon – 8PM

2 hour notification for 1 – 6 hour event Maximum10 events per year Capacity Pricing

2011/2012 $40,273 / MW-year 2012/2013 $6,008 / MW-year 2013/2014 $10,121 / MW-year 2014/2015 $45,797 / MW-year 2015/2016 $111,491 / MW-year

Existing 1993 Building thermostats stopped working Used State Pricing Contract to develop

specifications with local HVAC contractor to replace VAV boxes and controls along with installing VFD on fan and master control set back system

Upgrade resulted in monthly KWH savings of 50% to heat the administration building

ADS3 – Modify ADS1 as a merchant facility to accept FOG, organics, POTW sludge

Exporting Power Sale of RECs from ADS to local utility for

$150 K/ yr. SB 310 allows for Heat Recovery RECS

Applying for rebates & Gov. funding of projects.

Measure your facility’s electric load Assign a person or team to review your utility usage

an develop a strategy Start with the low hanging fruit / light controls,

HVAC ventilation controls, DO control The activated aeration process is usually 50% of the

facility’s electric load, so it is a good place to start. Look for government / utility funding for energy

projects. Look at using your facility’s emergency generators

to back up the utility

Ensuring a Sustainable Future: An Energy Management Guidebook for Wastewater and Water Utilities (USEPA)

Water and Wastewater Energy Best Practice Guidebook (WERF)

Evaluation of Energy Conservation Measures for Wastewater Treatment Facilities (USEPA)

Case Studies in Residual Use and Energy Conservation at Wastewater Treatment Plants (USEPA, National Renewable Energy Laboratory)

It’s never too late to start thinking about energy conservation/efficiency

Even a little savings now will compound over time

There are a lot of resources on the subject Know your system…you can’t fix or

improve what you don’t know Too much of a good thing sometimes isn’t

good

Questions? Brian M. Gresser, P.E.

BGresser@AkronOhio.gov Thomas F. Smith, P.E.

TFSmith@AkronOhio.gov

www.AkronOhio.gov/PubUtil/wpc